In recent years, high performance miniaturized dielectric resonators have been required for achieving the integration of microwave circuits.
The dielectric porcelain composition used for dielectric resonators requires a large relative dielectric constant .epsilon..sub.r and is wanted to constitute dielectric resonator having superior stability of a temperature coefficient .tau..sub.f of the resonance frequency, good linearity of temperature characteristics of the resonance frequency and a large unloaded Q value. As such a dielectric porcelain composition, there have heretofore been reported several compositions such as Ba(Zn.sub.1/3 Ta.sub.2/3)O.sub.3 -Ba(Mg.sub.1/3 Ta.sub.2/3)O.sub.3 described in the Japanese Patent Publication No. 59-51086, CaTiO.sub.3 -MgTiO.sub.3 -La.sub.2 O.sub.3.2TiO.sub.2 described in the Japanese Open-Laid Patent Application No. 53-98098, Sr(Zn.sub.1/3 Nb.sub.2/3)O.sub.3 -SrTiO.sub.3 described in the Japanese Patent Publication No. 50-34759 and Ba(Zn.sub.1/3 Nb.sub.1/3)O.sub.3 -Sr(Zn.sub.1/3 Nb.sub.2/3)O.sub.3 described in the Japanese Patent Publication No. 59-23045.
However, when a dielectric resonator to be used at a high frequency band such as 0.5-6 GHz is constituted using the above conventional ceramic compositions, there have been such drawbacks that (1) since their specific dielectric constants .epsilon..sub.r are small, it has been impossible to sufficiently miniaturize the resonator; (2) Q is small or the dielectric loss is large; and (3) since the temperature characteristics of the resonance frequency in the range of -40.degree. C.-60.degree. C. do not have a sufficient linearity, in other words, since the change in the resonance frequency accompanying the temperature change is not linear, it has become difficult to compensate the temperature characteristics, depending on the ambient conditions of the resonator (such as linear expansion coefficient of metal case or resonator support); hence it has been impossible to adjust the temperature coefficient of the resonance frequency of the whole of the resonance system to a sufficiently small value. For example, in the case of the ceramic compositions of e.g. Sr(Zn.sub.1/3 Nb.sub.2/3)O.sub.3 -SrTiO.sub.3, Ba(Zn.sub.1/3 Nb.sub. 2/3)O.sub.3 -Sr(Zn.sub.1/3 NB.sub.2/3)O.sub.3, etc., the values of Q, .epsilon..sub.r, etc. are almost satisfactory at a frequency band of 0.5-6 GHz, but there is a drawback that the linearity of the temperature characteristics is not sufficient.